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E.cpp
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E.cpp
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#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
bool flag = 0;
ll ans;
void dfs(vector<vector<int>> &adj, vector<bool> &visited, int u)
{
if (flag) return;
ans++;
if (ans >= 1000000) {
flag = 1;
return;
}
for (auto &v : adj[u]) {
if (!visited[v]) {
visited[v] = 1;
dfs(adj, visited, v);
visited[v] = 0;
}
}
}
void solve()
{
int n, m;
cin >> n >> m;
vector<vector<int>> adj(n + 1);
for (int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
vector<bool> visited(n + 1, 0);
visited[1] = 1;
ans = 0, flag = 0;
dfs(adj, visited, 1);
cout << ans << '\n';
}
int main()
{
#ifndef ONLINE_JUDGE
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
//freopen("Error.txt", "w", stderr);
#endif
ios_base::sync_with_stdio(false);
cin.tie(NULL), cout.tie(NULL);
int t = 1;
//cin >> t;
while (t--) solve();
return 0;
}